After decades of research, there is still no true consensus concerning the source or entry mechanism for
plasma sheet and ring current particles in the magnetosphere. This work addresses the long standing
problem by examining the source of magnetospheric plasma predicted by the multispecies version of the
BATS-R-US MHD code. Two Hydrogen species, one ionospheric in origin and one solar wind in origin, are
followed as they progress through the system during idealized simulations of various solar wind drivers. It is
found that the magnetosphere has two modes of convection and plasma entry that depend on the solar wind
conditions. During southward IMF, convection is reconnection-driven and the dominant source of plasma is
ionospheric particles entering near the tail reconnection point. During northward IMF conditions, viscous
interactions along the flanks of the magnetosphere drive convection and deliver large amounts of solar wind
plasma to the system. These results are examined further by performing real-event simulations and making
data-model comparisons using LANL Geosynchronous MPA particle data.

SM31B-02

Spectral Characteristics of Ions in the Earth's Plasmasheet: Statistical Results from Cluster CIS and RAPID

We present a statistical study of the spectral characteristics of protons in the Earth's plasma sheet for various
geomagnetic disturbance levels. The study is based on more than 2000 hours of data combined from the
Cluster RAPID and CIS instruments obtained during the tail season (July-October). Whereas the lower energy
range considered is typically well reproduced by Maxwellian energy spectra, the higher energies often deviate
significantly from such a distribution, and is better represented by a κ distribution. The actual spectral
slope depends on various magnetospheric driver parameters. During disturbed conditions, a significant
hardening of the spectra is observed. Periods with high solar wind pressure also characterized by a much
harder spectra. Unlike the electron spectra, we do not see any local time dependence in the proton spectra.

SM31B-03

Multi-satellite Investigations of the Cusps Under Various Pitch Angle Sorting Algorithms

The magnetospheric cusps are important conduits between the magnetosheath and ionospheric plasma
populations, however, their dynamic nature and large spatial size make them difficult regions of study. Previous
work by Keith and Stubbs [Adv. Space Res., Vol. 41, No. 10, 2008] to identify conjunctions in the cusps
between the Cluster and DMSP satellite missions have resulted in the two data sets currently under
investigation. The limited field of view of the SSJ/4 instruments on the DMSP spacecraft (F-6 through F-15)
means that the low-altitude data is always of downgoing (precipitating) particles. In contrast, the 3D nature of
the particle data sets of Cluster, together with their much higher altitude, require accurate pitch angle sorting of
the particle spectra as an important aspect of the data analysis. Multiple pitch angle sorting algorithms, both
those including bulk velocity and those ignoring it, will be subjected to similar analysis, noting the qualitative
and quantitative differences and the effects it may have on the conclusions that may be reached. This should
help determine the sensitivity of these data to the sophistication of the sorting method used and the
robustness of the analysis when being compared to low-altitude data.

* Rankin, R (rankin@phys.ualberta.ca), University of Alberta, Department of Physics, University of Alberta, Edmonton, AB
T6G2G7, Canada
Sydorenko, D (sydorenk@ualberta.ca), University of Alberta, Department of Physics, University of Alberta, Edmonton, AB
T6G2G7, Canada
Watt, C (cwatt@phys.ualberta.ca), University of Alberta, Department of Physics, University of Alberta, Edmonton, AB
T6G2G7, Canada

Observations from the NASA POLAR and FAST missions reveal that Alfven waves are intimately associated
with electron and ion particle acceleration in Earth's magnetosphere. Data from POLAR shows intense
geomagnetic field-aligned wave Poynting flux near and within the plasma sheet tail lobe boundary. The
corresponding UVI auroral imaging provides strong, but nevertheless circumstantial evidence that the
associated electron acceleration powers auroral emissions above the ionosphere. To explain the data, we
present results of modeling that agree with observations of Alfven wave activity, and describe the
characteristics of the resulting wave-particle interactions along the entire extent of a magnetic flux tube. Model
results using the Vlasov-Maxwell equations reveal detailed characteristics of the electron distribution functions
observed by POLAR, while two-fluid modeling of the resulting ion dynamics is shown to agree with
observations of up-flowing ion beams.
We argue that missions such as FAST and POLAR reveal the need for more detailed observations at high
altitude, on the order of 4-5Re. Such an opportunity is presented by the decision by Canada to launch two Polar
Communications Weather (PCW) satellites that sample the relevant region of Geospace within which
acceleration by Alfven waves is optimal. We discuss how a well-instrumented PCW mission would be used to
demonstrate closure on the nature of Alfven wave-induced particle acceleration.

Recent ion composition measurements near the magnetopause have shown that heavy ionospheric ions can
dominate the mass density as much as 30 percent of the time. Magnetopause transport processes, such as
reconnection, Kelvin-Helmholtz instability, and kinetic-scale Alfvenic fluctuations, can all be significantly affected
by the presence of heavy ions. Heavy ions modify the onset and growth of the tearing mode as well as reduce
the steady state reconnection rate by lowering the Alfven speed. Increased mass density reduces the effect of
magnetic tension and therefore lowers the Kelvin-Helmholtz instability threshold and increases the growth rate.
The presence of heavy ions can also increase the efficiency of mode conversion of compressional Pc3 waves
to transverse, field-aligned Alfven modes with small-scale structure perpendicular the the magnetopause. We
show that nonlinear heating and transport associated with mode converted waves will preferentially affect the
heavy ions. Because heavy ions can significantly influence physical processes at the magnetopause
associated with mass, momentum, and energy transport; we discuss how they could be used as a tool to
probe those physical processes responsible for the transport.

Field-aligned eigenmodes can be excited by mode conversion of compressional waves propagating across
magnetospheric field lines. For low frequencies, the mode conversion occurs at the Alfven resonance, but
mode conversion may also occur for higher frequencies at the ion-ion hybrid (IIH) resonance in multi ion
plasmas. Because the mode-converted waves at the IIH resonance are electromagnetic and have linear
polarization, it has been suggested as a mechanism to explain linearly polarized Pc 1-2 waves at Earth
magnetosphere. These waves propagate along the magnetic field and set up field-aligned eigenmodes
localized between the Buchsbaum resonances. The mode converted waves can also excite global Alfven
resonances that stand between the ionospheres. The aim of this study is to determine the dependence of the
eigenmodes of the mode-converted wave at the IIH resonance on the concentration of heavy ions in Earth
magnetosphere. To achieve this goal, we examine the eigenfrequencies of IIH resonances using the WKB
method. For this study, we use an axisymmetric dipole magnetic field model and empirical electron density
model between 3 and 9 Earth radii L shell. For different heavy ion concentration ratio, the eigenfrequencies and
their maximum latitudinal extent are presented. The results show that the linear polarized waves are localized
near the magnetic equator (less than 10 degree) and the frequency increases as the heavy ion concentration
ratio increases. We also compare the results with satellite observations of Pc 1-2 waves.

Geomagnetic pulsations are considered one of the modes of energy and momentum transfer between the
solar wind and magnetosphere, and different plasma regions within the magnetosphere. These ultra low
frequency (ULF) electromagnetic waves are usually identified using ground based magnetometer
measurements and are categorized based on frequency. In this study we have used eleven years of GOES
satellite geosynchronous magnetic field measurements to identify and characterize 1214 magnetic pulsation
events in the Pc4 and Pc5 bands. Local time of occurrence and frequency were recorded for each pulsation,
the latter using time-frequency spectral analysis. The local time distribution for pulsation occurrence showed a
broad dayside peak and the seasonal distribution indicated high pulsation occurrence in the winter months
compared to summer months. Pulsations also occurred over a wide range of frequencies, however discrete
frequency bands were observed in some individual events. These observations and their implications will be
discussed.

SM31B-08

THEMIS observations of magnetospheric ELF emissions, ULF Pc5 waves and their auroral features

Narrow-banded ELF/VLF emissions at about (n+1/2)fce, where fce is the electron gyrofrequency, are commonly
observed in the inner magnetosphere. They are generally believed to originate from an electron-cyclotron
harmonic instability due to an interaction between a "cold" (<100 eV) electron plasma and a "hot" (>1
keV) electron population. The hot component provides the local source of free energy for the instability growth,
while the cold electrons facilitate the propagation of the instability and control its spatial amplification. Such
ELF/VLF emissions are widely considered as a main candidate of driving the pitch-angle scattering and in turn
the precipitation of 1-10 keV electrons. In this presentation we report two events of strong ELF emissions near
3/2fce band at L∼10 in the postmidnight equatorial plasma sheet from recent THEMIS observations. Both
events occurred during the late substorm expansion phase and/or recovery phase, and the probes were
located at a couple of MLT hours east of the onset meridian determined from the ground auroral observations.
In one event the 3/2 fce emissions appeared in forms of discrete bursts modulated by a large-amplitude ULF
Pc5 waves with period 5-10 minutes. The Pc5 waves are identified as an eastward-propagating
poloidal/compressional waves, and non-FLR in nature. In the other event the 3/2 fce emissions appeared as a
somewhat continuous band lasting a few tens of minutes. On a inspection of the electron distribution functions
for both events we found that during the event intervals there was a coexistence of cold electron
population(∼10 eV), ambient plasma sheet electrons (1-2 keV), and enhanced energetic electrons
(>10 keV) presumably drifted from the injection region of the substorm, consistent with the theoretical
expectations. Conjugate auroral observations from THEMIS all-sky imagers, CGSM multi-spectral imagers,
CGSM meridian scanning photometers, and several higher time resolution white light imagers, reveal distinct
features such as eastward-drifting auroral patches and pulsating auroras with period of few seconds during
the event intervals. We attempt to relate those drifting patches and pulsating auroras to the in-situ observed
ELF emission and its resulting pitch-angle scattering process.